The relatively few cases of substance use disorders also influenced our data analysis. Because of the relatively few cases of substance use disorders in this study, we were forced to impose statistical constraints in order to empirically identify our models. Future studies with more cases of substance use disorders could extend our results by analyzing models without such statistical constraints. Elimination of these constraints, and the inclusion of more externalizing psychopathology diagnostic categories (e.g., antisocial personality disorder, conduct disorder, other substance use disorders) would be important in future studies.
